This invention relates to a method and apparatus for packing materials between foils of a synthetic material, of the type wherein a material to be packed is filled into a container formed in one foil web, and the space above the material is evacuated to remove oxygen containing gas prior to the sealing of the container with another foil web. The invention is particularly directed to the packing of materials which tend to splash when boiling.
Hot and liquid materials, especially prepared meals, should be packed in such a manner that the optimal quality of the material is preserved until it is to be consumed. In the past, food has commonly been permanently preserved by packaging in rigid tin cans, although at the present time it is becoming increasingly popular to package foods or meals by means of compound foils. Compound foil packages of synthetic material, which enclose prepared meals or parts of meals should be designed to preserve the material for a certain period of time. In addition, the packing should also be designed to be appealing, in order to promote the sales of the packages.
In one known device for packing foods in foils of synthetic material, a bottom foil web is fed from a first roll to a station in the device which includes a molding tool. The bottom foil web is heated, and then molded in the lengthwise and crosswise directions to form one or more rows of containers. These containers are then fed to a second station of the device, wherein they are filled with the desired material. The filled containers are then fed to a third station of the device. A top foil web is fed to the third station from a second roll and in the third station the top foil web is positioned over the bottom foil web. The filled container is then evacuated and the top foil web is sealed to the bottom foil web. The container is frequently heated to a high temperature following the sealing of the container, in order to sterilize the contents within the container.
When packing prepared meals or parts of meals, it is necessary to fill and pack the material at a temperature that is as high as possible, and also it is necessary to completely remove the air in the container. If the food is not hot just prior to sealing, there is a danger of reinfection of the food by microorganisms following the packaging thereof. It is to be noted that frequently the food being packaged is in liquid form or partly in liquid form.
It is further advantageous to pack the material while it is heated, in order to conserve thermal energy, since the pasteurization or sterilization process frequently immediately follows the packaging step.
In addition, the food being packed is frequently in a heated condition, since it may be filled in the containers just following a process of preparation. In the packaging of prepared meals and components thereof, it is desirable that the packing be effected in an air free manner, in order to obviate oxidation of food components such as fat, coloring, vitamins and flavoring.
It is also desirable to remove the air from the containers prior to sealing, since air bubbles or air inclusions in the food inhibit the transfer of heat energy within the food during any following treatment, such as sterilization or deep freezing, and also when the material is heated in the package prior to consumption.
U.S. Pat. No. 2,620,111 discloses the replacement of air in a packing container with steam or an inert gas. When the air in the container is replaced with steam, the steam condenses and a vacuum may be produced by this technique.
German Patent Publication 1,561,956 discloses a process for packing material between packing foils of a synthetic material, wherein the container is sealed by heat sealing the edges thereof following the removal of oxygen containing gas from above the material. Since materials to be packaged in this manner may tend to splash when boiling, a process of this type involves a risk that a portion of the filled material may splash during evacuation of the container, the splashing of the material onto the edges of the container rendering complete sealing of the edges of the container impossible.